This invention relates to a tamper switch for use, for example, as a switch for detecting the removal of a burglar alarm by an unauthorized person or as an interlock switch for electrical equipment.
Generally, burglar alarm devices such as an alarm horn designed to be attached to a wall are provided with a tamper switch for detecting the removal of the switch from the wall by an unauthorized person. The tamper switch is designed to be either turned on or turned off when it is detached from the wall. The opening and closing of such conventional tamper switch are rarely effected, and therefore it is necessary that the contact resistance of the tamper switch should be kept to a low level for a prolonged period of time to ensure that the tamper switch is not subjected to malfunction.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a tamper switch which can keep its contact resistance to a low level for a long period of time and can be manufactured at low costs.
According to the present invention, there is provided a tamper switch comprising a casing; an elongated tamper element mounted on the casing for movement along an axis thereof between an inoperative and an operative position, one end of the tamper element extending exteriorly of the casing; urging means for normally urging the tamper element into one of the operative and inoperative positions; a pair of elongated resilient contact plates mounted within and fixedly secured to the casing at their one ends, the pair of contact plates being disposed in generally parallel opposed relation to each other, each of the contact plates having a slit extending along a length thereof and opening to the other end thereof; and a contact element secured to the tamper element, the contact element being urged in between the pair of contact plates to make electrical contact therewith when the tamper element is brought into the operative position.